Effect of sowing of cultured fry on genetic structure of lagoon sea bass (Dicentrarchus labrax) populations assessed using amplified fragment lenght polymorphism analysis.

In these decades, we are assisting to the impoverishment of our marine ecosystem and the conservation of genetic diversity is becoming very important for the long-term interest of any species. In addition, the intensification of fish culture practises has increased the need to study genetic structure in cultured and wild fish stocks. Molecular markers have been very useful for analysis of genetic diversity. Among the several marker systems, amplified fragment lenght polymorphism (AFLP) is highly reliable for the assessment of genetic variation among and within populations. Until now, RAPD, microsatellites and mitochondrial haplotype analysis has been used to study the genetic diversity of sea bass. AFLP analysis was used to evaluate the effect of the sowing of fry obtained from intensive fish farm on the genetic structure of lagoon (Alimini, Otranto, LE) sea bass populations. As control we analysed the genetic structure of a sea bass lagoon population (Acquatina, Frigole, LE) where no fry sowing occurred. A group of 40 genotypes belonging to 2 populations was screened using 6 different AFLP primer combinations. A total of 366 loci were produced. Mean proportion of polymorphic loci of wild and extensive populations was 0.92 and 0.93, while mean expected heterozigosity was 0.37 and 0.36, respectively (Table 1). The genetic similarity valued based on Nei’s coefficient revealed an average population similarity of 92%. The individual-based similarity trees and the principal coordinate analysis revealed that the 2 populations were separated into two clusters. AMOVA analysis shows that a relatively high proportion of total genetic diversity was attributed within the groups (91.29%). AMOVA and Bayesian analysis was performed to evaluate FST and the two different analysis gave concordant results showing low genetic differentiation among Acquatina and Alimini populations (FST = 0.091; B = 0.0719, Table 2)